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Laser Process For Defining A Precision Resistor

IP.com Disclosure Number: IPCOM000048549D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Bergeron, DL: AUTHOR [+3]

Abstract

A process for trimming an ion-implanted resistor is provided wherein dopants in a semiconductor substrate located beneath a passivating layer. e.g., a layer of silicon dioxide, are activated by a continuous wave laser, such as an argon laser, scanning through the passivating layer in a direction perpendicular to the Intended flow of electrons in the resistor.

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Laser Process For Defining A Precision Resistor

A process for trimming an ion-implanted resistor is provided wherein dopants in a semiconductor substrate located beneath a passivating layer. e.g., a layer of silicon dioxide, are activated by a continuous wave laser, such as an argon laser, scanning through the passivating layer in a direction perpendicular to the Intended flow of electrons in the resistor.

After all high temperature steps for forming devices in a semiconductor substrate 10 have been completed and a passivating layer, such as a layer of silicon dioxide 12, is grown on the surface of substrate 10, resistor dopants are introduced into the surface of substrate 10 to form a resistor region 14 having a width W, as indicated in the figure. A pair of openings are formed in silicon dioxide layer 12 through which metal contacts are provided for the resistor defining the length L of the resistor, and the dopants are annealed at about 600
C.

To trim or adjust the value of the resistor a portion 16 of doped region 14 is scanned through silicon dioxide layer 12 by the continuous wave argon laser without damaging layer 12. The scanning is performed in a direction perpendicular to the length L of the resistor from one edge of resistor region 14 to the opposite edge thereof for a distance L' determined by the value of the resistance desired. To change the resistance by very small increments, a very finely focused laser beam, e.g., 2.5 micrometers, is preferred. F...